In the disclosure of the present invention reference is mostly made to the treatment of diabetes by delivery of insulin, however, this is only an exemplary use of the present invention.
Drug Injection devices have greatly improved the lives of patients who must self-administer drugs and biological agents. Drug Injection devices may take many forms, including simple disposable devices that are little more than an ampoule with an injection means or they may be highly sophisticated electronically controlled instruments with numerous functions. Regardless of their form, they have proven to be great aids in assisting patients to self-administer injectable drugs and biological agents. They also greatly assist care givers in administering injectable medicines to those incapable of performing self-injections.
In particular pen-style injection devices have proven to provide an accurate, convenient, and often discrete, way to administer drugs and biological agents, such as insulin. While pen-style injection devices are typically cylindrically shaped with a needle protruding from the most distal portion of one end of the device, some devices have other shapes with the needle no longer protruding from the most distal part of an end of the device, e.g. Innovo® and InnoLet® from Novo Nordisk A/S, Bagsvaerd, Denmark.
Typically, injection devices use a pre-filled cartridge containing the medication of interest, e.g. 1.5 or 3.0 ml of insulin or growth hormone. The cartridge is typically in the form of a generally cylindrical transparent ampoule with a needle pierceable septum at one end and an opposed piston designed to be moved by the dosing mechanism of the injection device. The injection devices generally are of two types: “Durable” devices and “disposable” devices. A durable device is designed to allow a user to replace one cartridge with another cartridge, typically a new cartridge in place of an empty cartridge. In contrast, a disposable device is provided with an integrated cartridge which cannot be replaced by the user; when the cartridge is empty the entire device is discarded.
Typical injection devices available today incorporates a dose setting feature where selection among a large variety of dose sizes may be performed by rotating a dose setting member. Although the dose selection thus provides for great flexibility and therefore being suitable for patients having different needs, the large variety in selecting the proper size of a dose may for some patients appear unnecessary complicated. This is especially the case for patients which are on a fixed dose regime. Also, from a safety point of view, the possibility of selecting a larger dose than intended may present a safety issue if a patient, such as a child performing a self-injection, by mistake adjusts the dose setting member for such an excessively large dose.
A series of recent publications relate to additional provisions for inclusion in manually injectors where an adjustable dose limiting element is incorporated to render the maximally selectable dose size adjustable, either by the individual patient or by the care-giver. Such dose limiting feature may be formed integral with the injection device as disclosed in U.S. Pat. No. 5,308,340, U.S. Pat. No. 5,514,097, US 2010/0324527 and in WO 2006/089767 A1.
Also, in particular for disposable devices, such dose limiting feature may be formed as an add-on which couples to the disposable device to limit the maximally selectable dose size. Examples of such devices are disclosed in U.S. Pat. No. 7,377,913 B2 and in WO 01/54757 A1.
While both the latter references provides the user with the possibility to limit the maximum selectable dose size from a disposable device by means of an add-on device, the maximum dose limit needs to be adjusted each time a new disposable injection device is to be put into use. Hence, such solutions require particular care each time the add-on device is mounted on the disposable device and there is a risk that the add-on will be not be used by the patient. A further limitation of those add-on devices is that they are limited for use with injection devices where the range of settable doses is limited to rotation within a single rotation.
Having regard to the above, it is an object of the present invention to provide a dose limiter module which enables a more user friendly operation of an associated medical injection device and which offers improvements in safety as compared with medical injection devices of the prior art.